workflow源码解析：ThreadTask

1、使用程序，一个简单的加法运算程序

#include <iostream>
#include <workflow/WFTaskFactory.h>
#include <errno.h>// 直接定义thread_task三要素
// 一个典型的后端程序由三个部分组成，并且完全独立开发。即：程序=协议+算法+任务流。// 定义INPUT
struct AddInput
{int x;int y;
};// 定义OUTPUT
struct AddOutput
{int res;
};// 加法流程
void add_routine(const AddInput *input, AddOutput *output)
{output->res = input->x + input->y;
}using AddTask = WFThreadTask<AddInput, AddOutput>;void callback(AddTask *task)
{auto *input = task->get_input();auto *output = task->get_output();assert(task->get_state() == WFT_STATE_SUCCESS);fprintf(stderr, "%d + %d = %d\n", input->x, input->y, output->res);
}int main()
{using AddFactory = WFThreadTaskFactory<AddInput, AddOutput>;AddTask *task = AddFactory::create_thread_task("add_task",add_routine,callback);AddInput *input = task->get_input();input->x = 1;input->y = 2;task->start();getchar();return 0;
}

2、类继承关系

WFThreadTaskFactory代码

// src/factory/WFTaskFactory.h
template<class INPUT, class OUTPUT>
class WFThreadTaskFactory
{
private:using T = WFThreadTask<INPUT, OUTPUT>;...
public:static T *create_thread_task(const std::string& queue_name,std::function<void (INPUT *, OUTPUT *)> routine,std::function<void (T *)> callback);...
};

// src/factory/WFTaskFactory.inl
template<class INPUT, class OUTPUT>
WFThreadTask<INPUT, OUTPUT> *
WFThreadTaskFactory<INPUT, OUTPUT>::create_thread_task(const std::string& queue_name,std::function<void (INPUT *, OUTPUT *)> routine,std::function<void (WFThreadTask<INPUT, OUTPUT> *)> callback)
{return new __WFThreadTask<INPUT, OUTPUT>(WFGlobal::get_exec_queue(queue_name),WFGlobal::get_compute_executor(),std::move(routine),std::move(callback));
}

__WFThreadTask代码

// src/factory/WFTaskFactory.inl
template<class INPUT, class OUTPUT>
class __WFThreadTask : public WFThreadTask<INPUT, OUTPUT>
{
protected:virtual void execute()  //实现ExecSession的纯虚函数{this->routine(&this->input, &this->output); //执行用户程序的routine}protected:std::function<void (INPUT *, OUTPUT *)> routine;public:__WFThreadTask(ExecQueue *queue, Executor *executor,std::function<void (INPUT *, OUTPUT *)>&& rt,std::function<void (WFThreadTask<INPUT, OUTPUT> *)>&& cb) :WFThreadTask<INPUT, OUTPUT>(queue, executor, std::move(cb)),routine(std::move(rt)){}
};

WFThreadTask代码

// src/factory/WFTask.h
template<class INPUT, class OUTPUT>
class WFThreadTask : public ExecRequest
{
public:void start();void dismiss();INPUT *get_input() { return &this->input; }OUTPUT *get_output() { return &this->output; }void *user_data;int get_state() const { return this->state; }int get_error() const { return this->error; }void set_callback(std::function<void (WFThreadTask<INPUT, OUTPUT> *)> cb);
protected:virtual SubTask *done();protected:INPUT input;OUTPUT output;std::function<void (WFThreadTask<INPUT, OUTPUT> *)> callback;public:WFThreadTask(ExecQueue *queue, Executor *executor,std::function<void (WFThreadTask<INPUT, OUTPUT> *)>&& cb) :ExecRequest(queue, executor),callback(std::move(cb)){// 初始化}protected:virtual ~WFThreadTask() { }
};

ExecRequest代码

// src/kernel/ExecRequest.h
class ExecRequest : public SubTask, public ExecSession
{
public:ExecRequest(ExecQueue *queue, Executor *executor);ExecQueue *get_request_queue() const { return this->queue; }void set_request_queue(ExecQueue *queue) { this->queue = queue; }virtual void dispatch()  // 实现SubTask的纯虚函数，这个纯虚函数主要是任务的开始执行接口{this->executor->request(this, this->queue);...}protected:int state;int error;ExecQueue *queue;Executor *executor;protected:virtual void handle(int state, int error); // 实现ExecSession的纯虚函数
};

SubTask代码

class SubTask
{// 子任务被调起的时机virtual void dispatch() = 0;// 子任务执行完成的时机virtual SubTask *done() = 0;// 内部实现，决定了任务流走向void subtask_done();...
};

ExecSession代码

/src/kernel/Executor.h
class ExecSession
{
private:virtual void execute() = 0;virtual void handle(int state, int error) = 0;protected:ExecQueue *get_queue() { return this->queue; }private:ExecQueue *queue;...
};

继承关系图

__WFThreadTask__目前还未用到，暂不清楚

3、两个重要成员: ExecQueue, Executor

ExecQueue代码

/src/kernel/Executor.h
class ExecQueue
{...
private:struct list_head task_list;pthread_mutex_t mutex;
};

Executor代码

/src/kernel/Executor.h
class Executor
{
public:// 一次要执行的接口，对于线程执行器来说，就是把一个执行任务扔进某个队列中int request(ExecSession *session, ExecQueue *queue);private:// 执行器和系统资源，是一个包含关系thrdpool_t *thrdpool;
};

request() 函数把任务扔进线程池队列等待执行，线程池会从队列拿到这个任务，然后执行executor_thread_routine

// src/kernel/Executor.cc
int Executor::request(ExecSession *session, ExecQueue *queue)
{ExecSessionEntry *entry = new ExecSessionEntry;session->queue = queue;entry->session = session;entry->thrdpool = this->thrdpool;queue->mutex.lock();list_add_tail(&entry->list, &queue->session_list);if (queue->session_list.next == &entry->list){struct thrdpool_task task = {Executor::executor_thread_routine, queue};/*{.routine	=	Executor::executor_thread_routine,.context	=	queue};*/if (thrdpool_schedule(&task, this->thrdpool) < 0){list_del(&entry->list);delete entry;entry = NULL;}}queue->mutex.unlock();return -!entry;
}

struct ExecSessionEntry
{struct list_head list;ExecSession *session;thrdpool_t *thrdpool;
};

// src/kernel/Executor.cc
void Executor::executor_thread_routine(void *context)
{ExecQueue *queue = (ExecQueue *)context;ExecSessionEntry *entry;ExecSession *session;queue->mutex.lock();entry = list_entry(queue->session_list.next, ExecSessionEntry, list);list_del(&entry->list);session = entry->session;if (!list_empty(&queue->session_list)){struct thrdpool_task task = {Executor::executor_thread_routine, queue};/*{.routine	=	Executor::executor_thread_routine,.context	=	queue};*/__thrdpool_schedule(&task, entry, entry->thrdpool);}elsedelete entry;queue->mutex.unlock();session->execute(); //这里会执行到用户routinesession->handle(ES_STATE_FINISHED, 0);
}

4、参考链接

https://github.com/chanchann/workflow_annotation/blob/main/src_analysis/12_thread_task.md
https://blog.csdn.net/j497205974/article/details/135554164?spm=1001.2014.3001.5502